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Diffstat (limited to 'docs/CANBUS.md')
| -rw-r--r-- | docs/CANBUS.md | 25 |
1 files changed, 21 insertions, 4 deletions
diff --git a/docs/CANBUS.md b/docs/CANBUS.md index 07569205..2446c533 100644 --- a/docs/CANBUS.md +++ b/docs/CANBUS.md @@ -6,10 +6,9 @@ Klipper currently only supports CAN on stm32 chips. In addition, the micro-controller chip must support CAN and it must be on a board that has a CAN transceiver. -To compile for CAN, run "make menuconfig", unselect "Use USB for -communication (instead of serial)" and then select "Use CAN for -communication (instead of serial)". Finally, compile the -micro-controller code and flash it to the target board. +To compile for CAN, run "make menuconfig" and select "CAN bus" as the +communication interface. Finally, compile the micro-controller code +and flash it to the target board. # Host Hardware @@ -41,6 +40,24 @@ iface can0 can static Note that the "Raspberry Pi CAN hat" also requires [changes to config.txt](https://www.waveshare.com/wiki/RS485_CAN_HAT). +# Terminating Resistors + +A CAN bus should have two 120 ohm resistors between the CANH and CANL +wires. Ideally, one resistor located at each the end of the bus. + +Note that some devices have a builtin 120 ohm resistor (for example, +the "Waveshare Raspberry Pi CAN hat" has a soldered on resistor that +can not be easily removed). Some devices do not include a resistor at +all. Other devices have a mechanism to select the resistor (typically +by connecting a "pin jumper"). Be sure to check the schematics of all +devices on the CAN bus to verify that there are two and only two 120 +Ohm resistors on the bus. + +To test that the resistors are correct, one can remove power to the +printer and use a multi-meter to check the resistance between the CANH +and CANL wires - it should report ~60 ohms on a correctly wired CAN +bus. + # Finding the canbus_uuid for new micro-controllers Each micro-controller on the CAN bus is assigned a unique id based on |